Algebramedium · Past Paper

Factorize a^2 - 10a + 21.

A(a-3)(a-7)
B(a+3)(a+7)
C(a-21)(a-1)
D(a-5)^2

✓ Correct Answer: A(a-3)(a-7)

Multiply to 21, add to -10: -3 and -7.

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